I have become addicted to painkillers and don't know what to do?

A few months ago, after a painful operation, the doctor put me on painkillers (combination of paracetamol= tylenol and codeine). The problem is that I kept taking them even after the pain subsided, because they made me feel better, and I felt I could perform better at work while I was on them. The codeine especially makes me feel more energetic. I tried to stop taking the tablets a few times, but felt so awful that I had to start again. I take at least 6 tablets a day and cannot imagine what to do without them. But I'd really like to stop because I know I am doing myself damage and I can't go on like that. By the way I don't drink or smoke, and used to be quite healthy before my addiction kicked in. Please give me some advice on how to stop without going crazy. Do I have to go cold turkey? And no judgmental answers please I will not even look at anything negative. Criticism is the last thing I need.